Manufacture of dental models.



UNIT D STATES PATENT oEFIoE.

.WILHELM NIELSEN, or BIELEFE'LD, GERMANY.

I mannmcrunn or DENTAL MonnLs.

No Drawing.

To all whom it may concern:

, Be it known that I, WILHELM NIELSEN,

a subject of the King of Denmark, residing at 7 Liitzowstrasse,Bielefeld, Germany,

have invented certain new and useful Imrovements in the Manufacture ofDental Klodels, of which the following is a specification.

This invention relates'to the manufacture of models for dentalpurposesfrom plaster of Paris.

As is well known it is usual in dental practice to take an impression ofthe interior of the mouth in plaster of Paris when accurate work isrequired as for example hen making bridges and the like. The de talcompositions which have hitherto been specially prepared for thispurpose have been found unsuitable for accurate work owing to theirliability to distortion and for this reason it is necessary to employplaster of Paris. As is well known the impression or negativethusobtained is employed for obtaining a positive plaster of Paris modelwhichis used in the further manufacture of theartificial denture orparts thereof.

Hitherto it has. been usual to employ differently colored plaster ofParis for the model and the impression so that the model could be moreeasily distinguished from the.

I was very tedious.

The object of the present invention is to obviate the foregoingdisadvantages and to enable the negative impression to be easlly and,accurately detached from the positive ohanical work.

model without the use of special tools or me- According to the presentinvention the im Specification of Letters Patent.

, manufacture of the artificial denture.

Patented Sept. '7, 1915.

Application filed October 17, 1913. Serial No. 795,642.

f pression ofthe interior of the mouth is taken in a composition whichconsists of plaster of Paris to which potato flour or an equivalentsubstance has been added in such proportion, preferably in theproportion of 4 parts of plaster of Paris to about 1 art of potatoflour, that the composition, when mixed with water or the like, forms apaste adapted to receive the impression and capable of hardening rapidlyand which when dry forms a firm impression, but which is asilydisintegrated in hot or boiling water or the like.

Thepositive 'model is obtained in the usual manner from the-ordinaryplaster of Paris which is insoluble on hardening and is obtained bypouring ordinary plaster of Paris over the negative impression which ispreferably covered with water glass to separate it from the model. Themodel is then obtained by immersing the whole in boiling water so thatthe negative impression detaches itself completely from the model in afew minutes and leaves a clean model which can be immediately used inthe further It will thus be seen that this method has the advantage thatno tool or mechanical appliance is necessary to remove the negativeimpression. Of course this method may also be employed when necessary toproduce negative .models from positive im ressions in which case thematerials would e interchanged.

I claim: 1

1. The method of obtaining a dental model which consists in obtaining anegative impression in a composition consisting of plaster of Paris andan additional agent and which composition on hardening is adapted todisintegrate in a hot liquid, ob-

taining a positive model therefrom in plaster of Paris anddetaching thenegative impression from the-positive model by immersing the negativeimpression in a hot liquid. L 5

2. The method of "bta-ining a dental model which consists in obtaining anegative impression in a composition consisting of plaster of Parisandpotato flour, obtaining a positive model therefrom in plaster of Parisand detaching the negative impression from the positive model byimmersing the negative impression in a hot liquid.

3. The method of obtaining a dental model which consists in obtaining anegative impression in a composition consisting of about 4 parts ofplaster of Paris to about 1 part of potato flour, obtaining a positivemodel therefrom in plaster of Paris and de- 7

